1. Field of the Invention
This invention relates to a hydraulic power system and, more particularly, to a hydraulic power unit for actuating blowout preventers of the type having shearing and shut-off rams.
Blowout preventers form a regular part of well drilling equipment as used, for example, in the drilling of oil wells and gas wells. Two major classes of blowout preventers are currently utilized to shut off uncontrolled flow of pressurized fluids: ram-type blowout preventers and spherical blowout preventers. In the ram-type blowout preventer, a hydraulic cylinder having a rod attached to its piston is utilized to move a ram, which acts as the closure element to close the passage of the pressurized fluid.
2. Description of the Prior Art
A combination shearing and shut-off ram for a blowout preventer is described in U.S. Pat. No. 3,736,982, issued June 5, 1973. This system is used in instances where a drill string must be cut and/or sealed to prevent damage to the well and associated equipment. It is important that the drill pipe be cut quickly. In order to shear some heavy wall, large diameter drill pipes, high pressures must be maintained on the rams while the shear rams are closed up against the drill pipe. Without this, there is the danger of not being able to shear the pipe or of damaging the rams.
It is the object of the present invention to provide a simple system for maintaining a high hydraulic pressure through the entire shearing sequence of the blowout preventer.